EP2831989B1 - Rectifier circuit with current injection - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to a rectifier circuit with a three-phase six-pulse rectifier arrangement of rectifying valves, preferably a bridge rectifier circuit of diodes, the rectifier arrangement having a three-phase mains-side input and a DC-side output, and at least one of three phases at the mains-side input with a first pole connection a three-pole circuit for deriving an injection current is connected into the three-pole circuit, according to the preamble of claim 1.

The present invention further relates to a method for impressing control currents in a DC-side output of a rectifier circuit with a three-phase six-pulse rectifier arrangement of semiconductor valves, preferably a three-pole bridge rectifier circuit of diodes, with an injection current of at least one of the three phases at a network-side input of the Rectifier circuit is branched off, according to the preamble of claim 18.

STATE OF THE ART

In modern power electronics, a large number of different embodiments of passive, active and mixed forms, so-called hybrid rectifier circuits, are known. The various rectifier circuits essentially provide a DC voltage that is as constant as possible at the output of the rectifier circuit from mains-side, sinusoidal voltages at the input. A frequently used rectifier arrangement is the three-phase (six-pulse) bridge rectifier arrangement (B6 circuit) of rectifier diodes known from the prior art, especially in power electronics after the bridge arrangement (the so-called DC side of the rectifier circuit) a rectified voltage is generated.

To reduce the pulse-shaped currents generated by the rectifier circuit at the input of the rectifier on the AC voltage side and to smooth the rectifier output voltage or the rectifier output current, inductances (chokes) on the DC voltage side are often connected between the rectifier output of the diode bridge and the output capacitor. In the case of rectifier circuits of the generic type, the rectifier current is passed through a choke connected to an output capacitor in parallel with the output in order to reduce distortions in the mains currents, and to reduce the curve of the To smooth the rectifier current and to provide a constant output voltage at the output or the output capacitor.

The line-side current curve of a rectifier circuit with switching elements, inductances and / or capacitances, even in operation with a passive (ohmic) load or another electronic circuit on the DC voltage side, is conventionally not sinusoidal. The non-sinusoidal currents cause unwanted line-side voltage or current distortions due to their harmonic content and the phase shift compared to the network fundamental. These network perturbations should not be neglected, particularly in the case of higher-power rectifier circuits. It is necessary to maintain a level of the total power of all harmonics in relation to the power of the fundamental (THDi, stands for "Total Harmonic Distortion of currents" or "total harmonic distortion of the currents"), whereby the maximum distortion of the mains currents and mains voltages by standards ( e.g. IEC61000-3-2) is specified.

It is known from the prior art that the current forms of the rectifier circuit can be influenced by adding or deriving currents, the so-called injection currents. In this case, currents are additionally impressed by additionally arranged switching elements, preferably in the currentless phases of the diode bridge currents. The current required for this is essentially three times the frequency of the network frequency, which means that this type of current injection to improve the network perturbations generated by the rectifier circuit is referred to in the literature as third harmonic current injection . The best-known representative of such a rectifier system and state of the art is the so-called Minnesota Rectifier .

The rectifier structure known in the art as Minnesota Rectifier uses an injection of a current with a third harmonic of the mains frequency simultaneously into all three phases of the AC connection of the rectifier circuit in order to achieve approximately sinusoidal mains currents of the rectifier circuit. As a result, those current gaps are filled which, due to the blocking effect of the rectifier arrangement, would not carry any current at the mains-side input. With a suitable choice of the injection current, the distortion of the mains currents can be avoided as far as possible and a better THDi can be achieved.

The circuit of the Minnesota Rectifier shows the main disadvantage that the currents required for this are impressed in all three phases at the same time and low-frequency loaded feed-in transformers have to be used which, due to the low-frequency load with the third harmonic of the mains frequency, have both a large volume and a large weight exhibit. When switching the Minnesota Rectifier, the injection current is generated by two step-up converter stages arranged on the DC voltage side. This allows a Regulated output voltage, which is filtered by a sufficiently large output capacitor, can be made available. By using the step-up converter on the DC side of the rectifier, however, two diodes are inserted into the primary power flow of the rectifier circuit, which results in a considerable reduction in efficiency, especially in the high power range. A selective injection of the required injection current only in that phase on the AC voltage side which would remain currentless in classic 6-pulse rectifier operation is possible, but requires additional active switches to select the respective phase. To do this, however, the injection current of the rectifier circuit must be adapted. However, such an operation is not possible with the topology of the Minnesota Rectifier. A comparable version was published in the publication " A Novel Three-Phase PFC Rectifier Using a Harmonie Current Injection Method "by Jun-Ichi Itoh et al. described.

Other rectifier circuits known from the prior art, which use the concept of third harmonic injection, can only be operated in parallel with the load of the rectifier circuit and without the use of the choke on the DC voltage side or without the use of a noteworthy output capacitor. In such existing circuits, in order to obtain approximately sinusoidal current, both the pulsating output voltage of the bridge rectifier and a constant power load, i.e. a load that consumes the required power independently of the voltages available, are required. Rectifier circuits with a technically advantageous choke and capacitance at the DC output cannot therefore be used. For the operation of many power electronic circuits, a sufficiently good smoothing and support of the output voltage and therefore a sufficiently large output capacitor is essential. Topologies of this type can therefore not be used in such applications. Further topologies can be found in the publication " A New Circuit Design and Control to Reduce Input Harmonic Current for a Three-phase AC Machine Drive System having a very small DC-link Capacitor "by the authors Hyunjae Yoo et al. described.

Further rectifier circuits were in the U.S. 5,784,269 A , EP 1 953 907 A1 , US 2004/160789 A1 as well as in the publication " A New Approach to Improve Power Factor and Reduce Harmonics in a Three Phase Diode Rectifier Type Utility Interface "by the authors Kim S. et al. described.

An essential, optimally possible rectification with simultaneous avoidance of network distortions is therefore not given in the case of rectifier circuits with current injection known in the prior art.

OBJECT OF THE INVENTION

It is therefore the aim of this invention to avoid these disadvantages and to improve a rectifier circuit with current injection as well as a method for impressing control currents in such a way that the rectifier circuit has low network perturbations, with an input current that is as sinusoidal as possible in phase with the respective network voltages , no large magnetic components are required on the AC voltage side of the rectifier circuit, pulse-shaped injection of the control current at the output of the rectifier circuit is avoided, no large AC voltage or DC voltage side arranged filter capacitors are required, and the efficiency of the rectifier circuit is improved.

DISCLOSURE OF THE INVENTION

These objects are achieved by the features of claim 1 and claim 18.

Claim 1 relates to a rectifier circuit with a three-phase six-pulse rectifier arrangement of semiconductor valves, preferably a bridge rectifier circuit of diodes, with a load, the rectifier arrangement having a three-phase mains-side input and a DC-side output comprising three switching elements and a three-pole circuit, and each phase of the mains-side input can each be switched on with a switching element to a first pole connection of the three-pole circuit for diverting an injection current into the three-pole circuit, and a second and third pole connection of the three-pole circuit are each connected to an output line of the DC-side output for control currents. According to the invention it is provided that the three-pole circuit is designed as a control circuit for active, independent control of at least two of the three currents given by control currents and injection current for generating sinusoidal rectifier input currents and controllable semiconductor valves, preferably IGBTs, for active control of at least two of the three currents provided by control currents and Injection current has given three currents, and a choke is arranged on one of the output lines of the DC-side output between the second pole connection and the load or between the third pole connection and the load at the DC-side output, and the load at the DC-side output is a time-variable load, wherein the control circuit for supplying the injection current is designed only in that phase which remains currentless due to the operation of the six-pulse rectifier arrangement.

In addition to the known rectifier arrangement, the circuit according to the invention has a three-pole circuit for impressing injection currents. Each individual phase of the network can be connected to the three-pole circuit by means of a switching element, whereby the so-called injection current is taken from the network and added to the rectifier currents as a control current. The circuit according to the invention enables operation with variable loads at the DC-side output of the rectifier circuit, since the control currents from the three-pole circuit with the aid of controllable semiconductor valves as active components for active regulation in the three-pole circuit can be regulated depending on the load. Passive components such as resistors, capacitors or inductors, as they are used in conventional circuit topologies of rectifier circuits using the injection principle, are not sufficiently suitable for this purpose. Controllable semiconductor valves in the form of IGBTs with anti-parallel freewheeling diodes are preferably provided as active components, but any type of switchable valve that can be used to control the switching states (e.g. MOSFETs, GTOs, ...). In the description of the present invention, the term controllable semiconductor valves is used to represent all controllable switching elements.

It is also possible to use a DC-side choke in combination with a sufficiently large output capacitor to obtain rectified, constant output voltages without impairing the function of the rectifier circuit and without causing high network distortions. The entire power of the rectifier circuit is fed through the choke at the output on the DC side. A voltage with alternating components that is produced by the rectifier arrangement can drop across the choke, with a rectified voltage remaining at the output and being able to be fed to the load. In particular, conventional rectifier circuits with a choke and output capacitor can be easily expanded by means of the three-pole circuit.

According to a further preferred embodiment of the invention, it is provided that the second and third pole connection of the three-pole circuit are each connected to one of the two output lines of the DC-side output via a second and third inductance, and the choke is provided between the second or third pole connection and the load is.

A differential voltage across the inductances forms the basis for regulating the control currents and the injection current. The respective currents, that is to say the control currents and / or the injection current, are set by modulating the active components in the three-pole circuit. The switching processes for modulating currents by means of active components are known per se in power electronics. The currents are smoothed by the inductances at the connections of the three-pole circuit and pulse-shaped currents can be avoided in the output on the DC side. As a result, expensive filter capacitors with large capacitance values are saved, which would absorb the pulse-shaped currents resulting from the switching process of the active components in a conventional manner. The throttle on The output on the DC side carries both the rectifier currents and the applied control currents and ensures continuous progression of the output variables.

In a further preferred embodiment of the invention it is provided that the first pole connection is connected to the switching elements via a first inductance, the three inductances being implemented by means of a 3-leg choke. The implementation of the three inductors by means of a conventional 3-leg choke represents a particularly space-saving, inexpensive and easy-to-implement variant, with each leg winding of the 3-leg choke forming an inductance.

According to a further embodiment of the rectifier circuit according to the invention, it is provided that the two output lines are connected to an output capacitor at the output on the DC side. This output capacitor essentially serves to maintain a constant output voltage in interaction with the choke, with an existing alternating component in the voltage loop between choke and output capacitor at the choke, and the output capacitor maintaining a constant, rectified output voltage. An output capacitor parallel to the output connection of the rectifier circuit is required, among other things, for the downstream operation of power electronic circuits such as a three-phase inverter stage.

In a further preferred embodiment of the invention, it is provided that each of the three phases is connected to a filter capacitor at the input on the network side, the filter capacitors being connected together in a star shape at a star point. It is also provided that the three-pole circuit is connected to the network-side input via at least one discharge capacitor. The diverting capacitor of the three-pole circuit, in combination with the star-shaped filter capacitors, forms an advantageous current path to divert currents caused by high-frequency switching processes in the three-pole circuit.

Furthermore, according to a further preferred embodiment of the invention, it is provided that the three-pole circuit comprises three converter systems with controllable semiconductor valves and / or a bidirectional switch, the first pole connection of the three-pole circuit on a first converter system and the second pole connection of the three-pole circuit on a second converter system Circuit, as well as the third pole connection of the three-pole circuit is provided on a third converter system, and a connection to a branch point, a common center point of the three-pole circuit, is provided from all three converter systems.

The three converter systems are used to impress the two control currents and the injection current with appropriate control. Each of the converter systems provides a degree of freedom for regulating the three flows, namely the two control flows and the injection flow. By means of the advantageous design of controllable half-liter valves and / or a bidirectional switch in a bridge structure, the degrees of freedom can be used to regulate the control currents.

Furthermore, according to a preferred embodiment of the invention, it is provided that the first converter system is provided as a 3-level bridge branch, the second and third converter systems being provided as half-bridges, and the three converter systems being implemented by means of three parallel-connected branches with electronic components are occupied, the first pole connection of the three-pole circuit being implemented on a first branch, and the second and third pole connections being implemented on a third branch, and each of the branches having a center connection around which center connections the components of the branches are symmetrically arranged, with a first midpoint connection of the first branch is connected to a second midpoint connection of the second branch via a bidirectional switch, and the second midpoint connection is conductively connected directly to a third midpoint connection of the third branch, the third midpoint point connection is provided as the center point of the three-pole circuit. The first converter system is designed as a 3-level bridge branch known per se, and can be provided unidirectionally or bidirectionally, as will be explained below. The converter systems two and three consist of two half bridges, but can also be designed as a three-stage or multi-stage bridge branch.

The first pole connection is provided on the first branch and the injection current flows into the first midpoint connection and thus into the three-pole circuit. The three branches connected in parallel in this way together represent the three converter systems as bridge structures, with which bridge structures the control currents and the injection current can be regulated.

Alternatively, according to a further preferred embodiment of the invention, it is provided that the three-pole circuit comprises two converter systems with controllable semiconductor valves, preferably arranged in a bridge structure, the second pole connection of the three-pole circuit on a second converter system and the third pole connection of the three-pole circuit is provided, and a connection to a branch point, a common center point, is provided by both converter systems, and the center point to the first pole connection connected is. According to this alternative embodiment of the invention, the first converter system is omitted and the first pole of the three-pole circuit is conductively connected directly to the center point of the two remaining converter systems.

According to a further preferred embodiment of the invention it is provided that the second and third converter systems are provided as half-bridges, the two converter systems being designed by means of two branches connected in parallel, and the first pole connection of the three-pole circuit being connected to a second branch, and to one third branch of the second and third pole connection are executed, and each of the branches has a center connection, around which center connection the components of the branches are symmetrically arranged, and a second center connection of the second branch is conductively connected directly to a third center connection of the third branch, wherein the third center point connection is provided as the center point of the three-pole circuit. According to this embodiment of the three-pole circuit, no first branch is provided, which is connected by means of a switch, but only an embodiment with two half bridges as converter systems, whereby two degrees of freedom are available for regulating the voltage and current variables of the bridge structures. The direct connection of the first pole of the three-pole circuit with the center point of the three-pole circuit and thus also of the two converter systems defines the potential at this point and both the two control currents and the injection current can be regulated with the two remaining converter systems.

To equip the branches with components, a further preferred embodiment provides that two buffer capacitors are connected in series on the second branch, the second center connection being arranged between the two buffer capacitors. Furthermore, it is provided according to a preferred embodiment that two bridge valves, preferably diodes, are connected in series with the same flow direction in the first branch, the first midpoint connection being arranged between the two bridge valves. Such an arrangement of diodes means a unidirectional design of the first converter system. A unidirectional design of the first converter system allows current to be carried only in one direction due to the diodes, which defines the transfer of energy from the network to the three-pole circuit. According to a further preferred embodiment it is provided that the two bridge valves are designed as controllable semiconductor valves, preferably IGBTs. Such an arrangement of controllable semiconductor valves instead of diodes means a bidirectional design of the first converter system. A bidirectional design of the first converter system allows, with suitable regulation of the three converter systems, to minimize the voltage across the buffer capacitors, since the currents required in the three-pole circuit is no longer limited by the flow direction of the bridge valves of the first converter system. This allows the maximum voltage of the buffer capacitors to be advantageously reduced.

According to a further preferred embodiment it is provided that the four controllable semiconductor valves are connected in series on the third branch, the center point of the three-pole circuit being arranged in the connection between two series-connected pairs of the controllable semiconductor valves, and the second pole connection between the controllable semiconductor valves of the first pair is provided, and the third pole connection is provided between the controllable semiconductor valves of the second pair. The control currents flow into the output lines on the DC side at these pole connections. The respective control currents can now be regulated through the two half bridges by suitable control of the controllable semiconductor valves. The voltages of the buffer capacitors used are decisive for the voltage ratios at the second and third pole connection and therefore also decisive for the ripple current occurring in the inductances.

According to a further preferred embodiment of the invention it is provided that the second center point connection is connected to the first pole connection via a voltage source. The second midpoint connection is directly connected to the midpoint. In order to be able to dynamically increase or decrease the potential of the center point of the three-pole circuit, the center point of the converter systems can be connected to the first pole connection via a voltage source. With the help of an increase or decrease in potential through the voltage source, the currents of the three-pole circuit can be regulated without distortion even with small potential differences, such as occur in principle with the direct connection of the first pole connection to the center of the converter systems.

In a further embodiment of the rectifier circuit according to the invention, it is provided that the second and third converter systems of the three-pole circuit are designed with bidirectional 3-level bridge branches known per se, preferably two so-called three-level neutral-point-clamped converters (3L-NPC), The 3-level bridge branches are arranged symmetrically around a midpoint branch connected in parallel to the 3-level bridge branches, and the midpoint branch is designed as two buffer capacitors connected in series, and the midpoint is provided between the two buffer capacitors, and a neutral connection of the 3-level Bridge branch is connected to the center point and the first pole connection, as well as an AC voltage connection of the 3-level bridge branch as the second pole connection and the third pole connection of the three-pole circuit are provided. The use of two 3-level bridge branches represents a particularly advantageous embodiment of the invention, since the first converter system is not required in this embodiment and thereby the efficiency of the entire rectifier system can be increased and the control currents can also be generated as distortion-free as possible. The regulation of the control currents can be achieved by activating the controllable semiconductor valves of the 3-level bridge arm, which is known per se, and the injection current results from the fact i _cp = i _h3 + i _cn . The embodiment described provides a bidirectional three-pole circuit.

According to a further preferred embodiment of the invention it is provided that the three-pole circuit with the first pole connection is connected to one side of two injection capacitors, which connection forms the center of the three-pole circuit, the other two sides of the injection capacitors being connected via a voltage source and Form connection points, each starting from the connection points a current loop with a buffer capacitor and a pair of controllable semiconductor valves being provided, and the second pole connection and the third pole connection being provided between the two controllable semiconductor valves of a pair. The regulation of the control currents is still carried out by suitable control of the two half bridges. If the amplitude of the voltages of the additional voltage source is high enough, this design allows the two control currents to be routed largely without distortion.

Claim 18 relates to a method for impressing control currents in a DC-side output of a rectifier circuit comprising three switching elements and a three-pole circuit according to claim 1 with a three-phase six-pulse rectifier arrangement of semiconductor valves, preferably a three-pole bridge rectifier circuit of diodes, with a load, wherein a Injection current of at least one of the three phases is branched off at a network-side input of the rectifier circuit. According to the invention it is provided that the injection current is fed to a first pole connection of the three-pole circuit, and an active, independent regulation of at least two of the three currents given by control currents and injection current for generating sinusoidal rectifier input currents with the help of active components, preferably controllable semiconductor valves, in the three-pole Switching takes place, whereby the injection current is only fed into the phase that remains de-energized due to the operation of the six-pulse rectifier arrangement, and a control current is added to the rectifier currents on two DC-side output lines of the DC-side output via a second and third pole connection of the three-pole circuit , and one of the rectifier currents with the control current supplied to it through one between the second pole connection and the load or between the third pole connection and the load at the output on the DC side is performed. The inductor current is composed of the rectified current and control currents. The choke in combination with the output capacitor smooths the output current and provides a constant output voltage. The injection current is only fed into the phase that would remain currentless due to the operation of the six-pulse rectifier arrangement and, with appropriate control, enables the generation of sinusoidal rectifier input currents in phase with the mains voltages, which lowers the mains perturbations of the rectifier structure. Since the additionally introduced three-pole circuit processes only a fraction of the energy of the entire rectifier circuit, a substantially better overall efficiency can be achieved in comparison to conventional low-reaction, active rectifier circuits. In particular, the method according to the invention offers the possibility of expanding existing conventional rectifier circuits and, with the expansion, operating them on the network with little reaction. It is also possible to operate a variable load at the output on the DC side by regulating the control currents, depending on the load, with known control of the active components.

According to a further preferred embodiment of the invention it is provided that the injection current and / or the control currents are passed through at least two of three inductors, provided on at least two of the three pole connections for smoothing and controlling the currents, through differential voltages across the inductors, and by means of regulation the third stream is set from two of the three streams.

With the method according to the invention, it is possible to operate rectifier circuits with low network distortions. The supplied control currents and the injection current are initially smoothed by the inductances without receiving pulse-shaped currents from the rectifier arrangement at the output. Large capacitances for filtering the pulses of the rectifying currents and any injection currents that are usual in rectifier circuits of this type are avoided. Furthermore, the differential voltage across the inductances is the basis for conducting currents through the inductances and thus in and out of the three-pole circuit. The sum of the currents at the pole connections of the three-pole circuit of the rectifier circuit according to the invention results in zero. High-frequency switching operations of the active components in the three-pole circuit result, in particular when all three currents are regulated at the pole connections, in high-frequency movements of a midpoint voltage of the three-pole circuit. An additional high-frequency current path can be provided by using additional bypass capacitors. In the present embodiment, however, it is provided that two of the three currents at the pole connections are regulated with the aid of active components in the three-pole circuit, the third current being zero due to the current sum.

According to a further preferred embodiment of the method according to the invention, it is provided that a midpoint voltage is measured between the midpoint of the three-pole circuit and a neutral point and an average value of the midpoint voltage is regulated with one of the converter systems. The measurement and filtering of the midpoint voltage, whereby the midpoint voltage is measured in relation to the neutral point (ground) of the network, allows the active regulation of this potential, which has advantages when generating the control currents and the injection current, since this potential controls the control currents or co-determines the injection flow. The potential difference, in particular that between the center point and the DC-side output lines and the mains-side input, is regulated with the aid of the active components in the three-pole circuit.

Another preferred embodiment of the invention provides that the first buffer capacitor voltage on the buffer capacitor is regulated to be greater than a voltage of the positive output line against a neutral point, and a second buffer capacitor voltage on the buffer capacitor is regulated to be lower than a voltage of the negative output line against the neutral point. The buffer capacitor voltages determine the differential voltages at the inductances of the pole connections when the controllable semiconductor valves are switched.

According to a further preferred embodiment, it is provided that the mean value of the midpoint voltage is regulated by means of the controllable semiconductor valves. According to a preferred embodiment of the invention it is provided that the mean value of the midpoint voltage is regulated to zero.

Due to the fact that the sum of all three currents of the three-pole circuit must necessarily be zero, it is sufficient if only two converter systems are used to regulate the control currents and the injection current, since the third current is mandatory. As a result, the remaining converter system can advantageously be used to regulate the midpoint voltage on average. Because of the time modulation, i.e. switching, of the controllable semiconductor valves, the mean value of the midpoint voltage should be used. The mean value of the midpoint voltage can be regulated by means of the active components in the three-pole circuit. The methods for controlling the active components or changing their switching states are known per se. If the midpoint voltage is regulated on average to zero in relation to the neutral point of the network, the amounts of the respective voltages on the buffer capacitors must be larger or smaller than those on the DC output lines opposite this midpoint can be impressed accordingly. According to a further embodiment of the method according to the invention it is provided that a first buffer capacitor voltage on the buffer capacitor is minimized and a second buffer capacitor voltage on the buffer capacitor is minimized, the midpoint voltage being regulated to the negative half the value of an injection voltage, and the injection voltage between the first pole connection and the Neutral point is applied. The voltages of the two buffer capacitors are minimized, with the midpoint voltage having to be regulated opposite to the voltage occurring at the first pole connection of the three-pole circuit against the neutral point. For this, however, a bidirectional design of the first converter stage is necessary, since the current and voltage of this converter system are not in phase in this embodiment.

In a further preferred embodiment of the method according to the invention it is provided for rectifier circuits according to claim 11 or 17 that the potential of the midpoint voltage is increased or decreased with respect to one of the two output lines with the aid of the regulation of the voltage source. This is provided in order to obtain sufficiently large potential differences for regulating the control currents at the pole connections. This ensures that the control currents and the injection current are routed without distortion, which subsequently leads to distortion-free input currents of the rectifier circuit.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1

eine herkömmliche Ausführungsform einer Gleichrichterschaltung mit Drossel,

Fig. 2

eine bevorzugte Ausführungsform einer erfindungsgemäßen Gleichrichterschaltung mit drei Konvertersystemen,

Fig. 3

eine bevorzugte Ausführungsform einer erfindungsgemäßen Gleichrichterschaltung mit zwei Konvertersystemen,

Fig. 4

eine bevorzugte Ausführunsgform einer erfindungsgemäßen Gleichrichterschaltung mit Drossel,

Fig. 4a

den Verlauf der dreiphasigen Netzströme am netzseitigen Eingang der erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 4b

den Verlauf einer Ausgangsspannung sowie einer gleichgerichteten Spannung am gleichstromseitigen Ausgang einer erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 4c

den Verlauf eines positiven Gleichrichterstroms der erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 4d

den Verlauf eines Injektionsstroms der erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 4e

den Verlauf eines negativen Gleichrichterstroms der erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 4f

den Verlauf eines Drosselstroms einer erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 4g

den Verlauf eines Steuerstroms einer erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 4h

den Verlauf eines Steuerstroms einer erfindungsgemäßen Gleichrichterschaltung gemäß Figur 4,

Fig. 5

eine Ausführungsform der dreipoligen Schaltung der erfindungsgemäßen Gleichrichterschaltung mit Drossel,

Fig. 6

eine weitere bevorzugte Ausführungsform einer erfindungsgemäßen Gleichrichterschaltung mit Drossel,

Fig. 6a

den Verlauf des Mittelwerts einer Mittelpunktspannung der erfindungsgemäßen Gleichrichterschaltung gemäß Figur 6 bei erfindungsgemäßer Einprägung eines Steuerstroms,

Fig. 7

eine weitere bevorzugte Ausführungsform einer erfindungsgemäßen Gleichrichterschaltung mit Drossel,

Fig. 8

eine weitere Ausführungsform der dreipoligen Schaltung der erfindungsgemäßen Gleichrichterschaltung mit Drossel, sowie

Fig. 9

eine weitere Ausführungsform der dreipoligen Schaltung der erfindungsgemäßen Gleichrichterschaltung mit Drossel.

The invention is explained in more detail below on the basis of exemplary embodiments with the aid of the accompanying drawings. It shows here the

Fig. 1

a conventional embodiment of a rectifier circuit with a choke,

Fig. 2

a preferred embodiment of a rectifier circuit according to the invention with three converter systems,

Fig. 3

a preferred embodiment of a rectifier circuit according to the invention with two converter systems,

Fig. 4

a preferred embodiment of a rectifier circuit according to the invention with a choke,

Figure 4a

the course of the three-phase line currents at the line-side input of the rectifier circuit according to the invention Figure 4 ,

Figure 4b

the profile of an output voltage and a rectified voltage at the DC-side output of a rectifier circuit according to the invention according to Figure 4 ,

Figure 4c

the course of a positive rectifier current of the rectifier circuit according to the invention according to Figure 4 ,

Figure 4d

the course of an injection current of the rectifier circuit according to the invention according to Figure 4 ,

Figure 4e

the course of a negative rectifier current of the rectifier circuit according to the invention according to Figure 4 ,

Fig. 4f

the course of a choke current of a rectifier circuit according to the invention according to Figure 4 ,

Fig. 4g

the course of a control current of a rectifier circuit according to the invention according to Figure 4 ,

Fig. 4h

the course of a control current of a rectifier circuit according to the invention according to Figure 4 ,

Fig. 5

an embodiment of the three-pole circuit of the rectifier circuit according to the invention with a choke,

Fig. 6

another preferred embodiment of a rectifier circuit according to the invention with a choke,

Figure 6a

the course of the mean value of a midpoint voltage of the rectifier circuit according to the invention according to Figure 6 when a control current is impressed according to the invention,

Fig. 7

another preferred embodiment of a rectifier circuit according to the invention with a choke,

Fig. 8

a further embodiment of the three-pole circuit of the rectifier circuit according to the invention with a choke, as well as

Fig. 9

a further embodiment of the three-pole circuit of the rectifier circuit according to the invention with a choke.

WAYS OF CARRYING OUT THE INVENTION

The Fig. 1 shows a known rectifier circuit with a rectifier arrangement 1 of semiconductor valves 2, a (six-pulse) bridge rectifier arrangement with diodes, and with a DC-side choke 7. The rectifier circuit comprises a line-side input 3 and a DC-side output 4, with phases U, at line-side input 3. V, W are executed, and at the DC-side output 4 a positive output line P _DC and a negative output line N _DC . A rectified voltage U _{rec is applied} to the rectifier arrangement 1, a constant output voltage U ₀ being produced at the output.

In the Figure 1 a neutral point N, the ground potential of the network, is shown on the network side. At the output 4 on the _{DC side} , a load 6, shown as a variable resistor, is connected to the output lines P DC, N _{DC, which loads a time-variable power P o} (t). Furthermore, an output capacitor C _{0 is} usually provided at the output 4 on the DC side between the output lines P _DC , N _DC. The load 6 is not shown in the other figures, since the connection is at the same point in each case as in FIG Figure 1 he follows. The load 6 can also be a further electronic circuit, for example a further current converter, the rectifier circuit shown then being used as a so-called rectifier with a voltage intermediate circuit. The entire power of the load 6 is transported via the choke 7 from the mains to the rectifier output, the half-waves of the output voltage typical for the illustrated three-phase diode bridge with semiconductor valves 2 being smoothed _{by a choke 7 in combination with an output capacitor C 0.}

In the Figure 1 However, the rectifier circuit shown has a design which is disadvantageous with regard to network perturbations. The rectifier circuit has, depending on the dimensioning of the arranged choke 7, more or less pulse-shaped input currents with currentless gaps at the network-side input 3 and therefore cause undesirable network perturbations, whereby a possibly required THDi of the input currents can usually not be achieved.

In order to improve the THDi, a rectifier circuit according to the invention is shown in FIG Figure 2 and Figure 3 intended. The rectifier circuit according to the invention with a rectifier arrangement 1 also has a three-pole circuit 5. The three-pole circuit 5 has a first pole connection A, a second pole connection B and a third pole connection C. The first pole connection A can be switched on with switching elements S ₁ , S ₂ , S ₃ at least to one phase U, V, W at the line-side connection. The second pole connection B is connected to the positive output line P _DC , to be precise even before the choke 7 establishes the connection to the load 6. The third pole connection C is connected to the negative output line N _DC .

In Figure 2 a rectifier circuit according to the invention with a first converter system 9, a second converter system 10 and a third converter system 11 is shown. The three-pole circuit 5 is constructed with converter systems 9, 10, 11, the first converter system 9 being connected to the pole connection A, a second converter system 10, a third converter system 11, and a center point M. The second converter system 10 is connected to the pole connection B and the center point M, the third converter system 11 being connected to the pole connection C and the center point M. At least two of the converter systems 9, 10, 11 have controllable semiconductor valves S _{cp +} , S _cp- , S _{cn +} , S _cn- for the active regulation of control _{currents i cp} , i _cn and / or an injection current i _h3 . The first converter system 9 is designed as a unidirectional or bidirectional 3-level bridge branch, the second and third converter systems 10, 11 being designed as half bridges.

In Figure 3 a rectifier circuit 1 according to the invention with a second converter system 10 and a third converter system 11 is shown. A first converter system 9 is not provided, but the first pole connection A is connected directly to the center point M. The converter systems 10, 11 have controllable semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _cn- for the active regulation of control _{currents i cp} , i _Cn and / or an injection current i _h3 .

The switching elements S ₁ , S ₂ , S ₃ each have a phase U, V, W connected to the pole connection A of the three-pole circuit 5, a current path being made available for the one injection current i _h3 . _{Control currents i cp} , i _cn flow via the pole connections B, C to the output 4 on the DC side. At the input 3 on the network side, the injection of the injection _{current i h3} prevents network distortion. The injection current required for sinusoidal input currents is composed as in the Figures 4a to 4e can be seen from sections of the desired sinusoidal input currents and has as in the Figure 4d shown approximately triangular course.

The three-pole circuit 5 according to the preferred embodiment of a rectifier circuit according to the invention Figure 4 uses a unidirectional 3-level bridge _{branch consisting of the two rectifier diodes D h3 +} and D _h3- on a first branch Z ₁ and a bidirectional switch S _h3 from a first midpoint connection M ₁ to a second midpoint connection M ₂ , to implement the first converter system 9 the diodes D _{h3 +} , D _{h3- connect} the first center point connection M ₁ to the positive and negative connections of the buffer capacitors C _CP , C _CN , which buffer capacitors are provided on the second branch Z ₂ . The bidirectional switch S _{h3 connects} the first center point connection M ₁ to the second center point connection M _{2 by} switching on the bidirectional switch S _h3 and thus also to the center point M of the three-pole circuit 5 via a conductive connection. The second converter system 10 and the third converter system 11 are provided by two half bridges with the four controllable semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _cn- , the positive and negative connections of the two half bridges with the buffer capacitors C _CP , C _CN are connected. The semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _cn- are provided on a third branch Z3. The implementation of such an interconnection of controllable semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _cn- is possible in particular with a so-called "3-level topology" of IGBTs with freewheeling diodes which is available on the market and can therefore be implemented cheaply, with a center point M is also provided. The buffer capacitors C _CP , C _CN are both part of the 3-level bridge arm of the first converter system 9 and the half bridges of the second and third converter systems 9, 10. The pole connections B and C of the three-pole circuit are each provided between a first pair S _{cp +} , S _cp- and a second pair S _{cn +} , S _cn- of controllable semiconductor valves. _{The currents i h3} , i _cp , i _{cn can be} regulated by suitable control of the controllable semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _{cn- of} the two half bridges and the 3-level bridge branch.

Furthermore, the preferred embodiment of the rectifier circuit according to the invention according to FIG Figure 4 at the mains input 3 with the phases U, V, W connected, star-shaped arranged filter capacitors C _F. The filter capacitors C _F are arranged in a star shape around a star point M _CF. The star point M _CF is also connected to a discharge capacitor C _BF with a center point M of the three-pole circuit 5. This connection of the mains-side input 3 to a discharge capacitor C _BF via the filter capacitors C _F allows high-frequency fault currents i _f , arising from the high-frequency switching operations in the three-pole circuit 5, to flow away, which is particularly advantageous when all three currents i _h3 , i _cp , and i _{cn of} the three-pole circuit 5 are regulated with a specially designed controller. The connection of the Diverting capacitor C _BF is not, however, viewed as a further, fourth pole connection of the three-pole circuit 5, since the diverted fault currents i _{f are} high-frequency and comparatively small compared to the currents in the pole connections A, B, C.

Each of the pole connections A, B, C is according to a preferred embodiment in Figure 4 connected to an inductance L _h3 , L _cp , L _cn , which are used to carry the two control currents i _cp , i _cn and the injection _{current i h3} . In this way, at least two of the three currents i _h3 , i _cp , i _{cn are} regulated, the third current being zero due to the mandatory current sum.

The Figure 4a shows the current curve of the phases U, V, W at the input 3 on the network side. The phase currents i _u , i _v , i _w are phase-shifted according to a three-phase network.

The Figure 4b shows the rectified voltage U _rec which is applied between the two output lines P _DC , N _DC after the rectifier arrangement 1. The rectified voltage U _rec has sinusoidal peaks in addition to an output voltage U _0. By filtering the rectified voltage U _rec with the choke 7 and the output capacitor C ₀ , a constant output voltage U _{0 is} achieved.

The Figure 4c shows the course of a positive rectifier _{current i p} , which results from a suitable supply of a control current i _cp to the positive output line P _{DC of} the bridge rectifier. The sine peaks shown correspond to the respective sections of the sinusoidal input currents i _u , i _v , i _w .

In Figure 4d the injection current i _{h3 is} shown, which corresponds to the triangular components of the network currents i _u , i _v , i _w. With the rectifier circuit according to the invention, this injection current i _{h3 is} fed to the three-pole circuit 5.

The inductor current i _L is in Figure 4f shown and has a constant output current i ₀ which is fed directly to the load 6, and a superimposed alternating component which results from the voltage difference between the rectifier _{output voltage U rec} and the approximately constant output voltage U ₀ . The course of the required control currents i _cp , i _cn is in the Figures 4g and 4h The control currents i _cp , i _cn are preferably shown in FIG Figure 4g and Figure 4h to regulate.

According to a further embodiment, a second and third converter system 9, 10 of the three-pole circuit 5 can be provided. The first converter system 9 is connected by a direct connection to the pole connection A via the center point M. The second and third converter system 10, 11 is, as already in Figure 4 described, advantageously carried out by half bridges with controllable semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _cn- and buffer capacitors. The direct connection of the center point M to the pole connection A of the three-pole circuit 5 defines the potential of the center point M and does not show any high-frequency voltage jumps. The two control currents i _cp , i _{cn are} regulated by suitable control of the controllable semiconductor valves of the two half bridges and, the injection _{current i h3} resulting from the current sum of zero of the three-pole circuit 5. A connection of the three-pole circuit 5 by means of discharge capacitor C _BF back to the network is according to the embodiment of the rectifier circuit according to FIG Fig. 3 not provided.

In Figure 5 an advantageous embodiment of the three inductors L _h3 , L _cp , L _cn with a three-leg choke is indicated, the direction of the winding being entered with points on the individual chokes, which advantageously results in a significant reduction in the structural volume and weight of the magnetic components and thus of the entire rectifier system according to the invention.

Furthermore, in the Figure 5 An embodiment of the bidirectional switch S _{h3 of} a unidirectional 3-level bridge arm of the first converter system 9 of a three-pole circuit 5 is shown, in which two IGBTs connected against one another with anti-parallel freewheeling diodes are used, although other switch elements such as MOSFETs can also be used as an alternative. This design of bidirectional switches S _h3 is known per se, but is to be illustrated here in conjunction with the rectifier circuit according to the invention, with the regulation of a midpoint voltage U _{MN in conjunction with the bidirectional switch S h3 with the rectifier circuit according to the invention and the method according to the invention for impressing control currents} should be explained.

The midpoint voltage U _MN , shown in Figure 5 and Figure 6 , influences the generation of the differential voltages U _L3 , U _Lp , U _Ln across the inductances L _h3 , L _cp , L _{cn in} order to regulate the control currents and / or the injection current. The first differential voltage U _L3 results from the first inductance L _h3 etc. An injection _{voltage U h3} results from the potential of the first pole connection A with respect to the network, i.e. with respect to the neutral point N.

• -) Es werden alle drei Ströme i_h3,i_cp,i_cn simultan mit drei Konvertersystemen 9,10,11 auf einen gewünschten Verlauf geregelt. Eine Regelung der Mittelpunktspannung U_MN ist dabei nicht möglich, da alle Freiheitsgrade der erfindungsgemäßen Gleichrichterschaltung bereits zur Regelung verwendet werden. Bei eventuell auftretenden Regelfehlern treten Potentialsprünge der Mittelpunktspannung U_MN in Erscheinung die vorteilhaft durch eine Ausführung mit Ableitkondensator C_BF eingefangen werden können.
• -) Es werden jeweils nur zwei der drei Ströme i_h3,i_cp,i_cn mit den jeweiligen Konvertersystemen 9,10,11 geregelt, wobei z.B. das Konvertersystem 9 den Injektionsstrom i_h3 und das Konvertersystem 10 den Steuerstrom i_cp regelt. Aufgrund des prinzipgedingten Umstandes, dass die Stromsumme der dreipoligen Schaltung null ist, wird das dritte Konvertersystem 11 vorteilhaft dazu verwendet um den Mittelwert der Mittelpunktspannung U_MN zu regeln.
• -) Gemäß einer weiteren bevorzugten Ausführungsform ist eine Minimierung der Pufferkondensatorspannungen U_cp,U_cn möglich, indem der Mittelwert der Mittelpunktspannung U_MN gegengleich zur am ersten Polanschluss A der dreipoligen Schaltung 5 auftretenden Injektionsspannung U_h3 geregelt wird. Es werden wieder jeweils nur zwei der drei Ströme i_h3,i_cp,i_cn mit den jeweiligen Konvertersystemen 9,10,11 geregelt, wobei z.B. das Konvertersystem 11 den Injektionsstrom i_h3 und das Konvertersystem 9 den Steuerstrom i_cp regelt, wobei das dritte Konvertersystem 10 dann zur Regelung des Mittelwertes der Mittelpunktspannung U_MN herangezogen wird. Beispielhaft ist in Figur 6a solch eine, gegengleich zur Spannung am ersten Polanschluss A der dreipoligen Schaltung 6 geregelter Mittelwert der Mittelpunktspannung U_MN eingezeichnet, wobei in Figur 6a nur die über eine Schaltperiode der Halbleiterventile S_cp+,S_cp-,S_cn+,S_Cn-,S_h3,S_h3+,S_h3- gemittelte Mittelpunktspannung, dargestellt ist.

Options for regulating the injection of control currents according to the invention are summarized below:

• -) All three currents i _h3 , i _cp , i _{cn are} regulated simultaneously with three converter systems 9, 10, 11 to a desired course. A regulation of the midpoint voltage U _MN is not possible, since all degrees of freedom of the rectifier circuit according to the invention are already used for regulation. If control errors occur, potential jumps in the midpoint voltage U _MN appear, which can advantageously be captured by a design with a discharge capacitor C _BF.
• -) Only two of the three currents i _h3 , i _cp , i _{cn are} regulated with the respective converter systems 9, 10, 11, with the converter system 9 regulating the injection _{current i h3} and the converter system 10 regulating the control current i _cp , for example. Due to the fact that the current sum of the three-pole circuit is zero, the third converter system 11 is advantageously used to regulate _{the mean value of the midpoint voltage U MN.}
• According to a further preferred embodiment, the buffer capacitor voltages U _cp , U _{cn can} be minimized by regulating the mean value of the midpoint _{voltage U MN in opposition to the injection voltage U h3} occurring at the first pole connection A of the three-pole circuit 5. Again, only two of the three currents i _h3 , i _cp , i _{cn are} regulated with the respective converter systems 9, 10, 11, the converter system 11 regulating the injection _{current i h3} and the converter system 9 regulating the control current i _cp , with the third Converter system 10 is then used to regulate the mean value of the midpoint voltage U _MN . An example is in Figure 6a _{such a regulated mean value of the midpoint voltage U MN} , which is opposite to the voltage at the first pole connection A of the three-pole circuit 6, is shown in FIG Figure 6a _{only the midpoint voltage} averaged over a switching period of the semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _Cn- , S _h3 , S _{h3 +} , S h3- is shown.

While the first converter system 9 can be designed with a unidirectional 3-level bridge branch for the first two control methods, a bidirectional execution of the 3-level bridge branch of the first converter system 9 is absolutely necessary for the third control method.

In Figure 6 a preferred embodiment of the three-pole circuit 5 with a bidirectional 3-level bridge branch in the first converter system 9 is shown. The rectifier diodes D _{h3 +} , D _h3- on the first branch Z ₁ , as in FIG Figure 4 shown, by active controllable semiconductor _{components S h3 +} , S h3-, for example as in Figure 6 shown by IGBTs with anti-parallel freewheeling diodes. As a result, currents can also be _{impressed in phase opposition to the injection voltage U h3} at the first pole connection A of the three-pole circuit 5.

The Figure 7 shows an embodiment of the rectifier circuit according to the invention, wherein the first converter system 9 is replaced by a direct connection of the first pole connection A to the center point M of the three-pole circuit 5, and both the second converter system 10 and the third converter system 11 are implemented by a 3-level bridge branch is, where in Figure 7 the known three-level neutral-point-clamped converter 3L-NPC is designed, where generic bridge branches can also be used. The two 3-level bridge branches are each arranged symmetrically around a midpoint branch Zm, the midpoint branch being connected to the DC voltage connections of the 3-level bridge branches. The midpoint branch Z _m is provided with buffer capacitors C _CP , C _CN and can be connected directly to the midpoint M of the midpoint branch Z _m with the network-side input 3 via the switching elements S ₁ , S ₂ , S _3. A neutral connection N _{8 of} the 3-level bridge branches is connected to the center point M and the first pole connection A. An alternating voltage connection AC _{8 of} the 3L-NPC is connected to the pole connections B, C _{via the inductances L CP} , L _CN. In this embodiment, the control currents i _cp , i _{cn are} regulated by suitable control of the semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _{cn- of} the 3-level bridge _{branches, the injection current i h3 being obtained} automatically. Since the center point M is connected directly to the network phases U, V, W via the switches S1, S2, S3, there is no need to regulate the medium voltage U _MN . Since the control currents i _cn , i _{cp have} both positive and negative signs with an always positive or negative voltage level at the center point M, bidirectional bridge structures must be used in the two converter systems 10, 11.

The Figure 8 shows a further embodiment of the three-pole circuit 5, a voltage source U _{x being} additionally provided _{on the branch of the injection current i h3.} The control currents i _cp , i _cn are regulated by suitable activation of the controllable semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _{cn- of} the converter systems 10, 11, the injection _{current i h3 being obtained} automatically. According to the _{invention, the voltage source U x} impresses a time-variable voltage in the branch between the pole connection A and the midpoint M of the three-pole circuit, which increases or reduces the midpoint voltage U _MN and enables the control currents i _cp , i _cn to be routed with little distortion .

In Figure 9 a further embodiment of a three-pole circuit 5 with voltage source U _{x is} shown, which is provided between the second and third converter systems 10, 11 of the three-pole circuit, the voltage source U _x according to FIG Figure 9 is a DC voltage source. In parallel to the voltage source, two injection _capacitors C h3p, C _{h3n are} provided, their connection to the pole connection A of the three-pole circuit 5 is connected. The control currents i _cp , i _cn are regulated by suitable activation of the controllable semiconductor _{valves S cp +} , S cp-, S _{cn +} , S _cn- , the injection _{current i h3} automatically resulting from the current sum zero. The additionally inserted voltage source U _x advantageously lowers the negative potential of the second converter system 10 or increases the potential of the positive terminal of the third converter system 11, which subsequently _{enables the two control currents i cn} , i _cp to be routed largely without distortion.

It is thus immediately apparent that a rectifier circuit with current injection and a method for impressing control currents have been improved in such a way that the rectifier circuit has low network perturbations, with an input current that is as sinusoidal as possible in phase with the respective network voltages, no large magnetic components are required on the AC voltage side of the rectifier circuit, pulse-shaped injection of the control current at the output of the rectifier circuit is avoided, no large AC voltage or DC voltage side arranged filter capacitors are required, and the efficiency of the rectifier circuit is improved.

List of reference symbols:

1

Rectifier arrangement

2

Semiconductor valve

3

mains-side input

4th

DC-side output

5

three-pole circuit

6th

load

7th

throttle

A.

first pole connection

AC8

AC voltage connection

B.

second pole connection

C.

third pole connection

C0

Output capacitor

CBF

Bypass capacitor

CF

Filter capacitor

Ccp

Buffer capacitor

Ccn

Buffer capacitor

Ch3p

Injection capacitor

Ch3n

Injection capacitor

Qh3 +

Bridge valve

Qh3-

Bridge valve

ih3

Injection current

icn

Control current

icp

Control current

iL

Choke current

ip

positive rectifier current

in

negative rectifier current

if

Fault current

iu

Phase current

iv

Phase current

iw

Phase current

Bh3

first inductance

Lcp

second inductance

Lcn

third inductance

M1

first midpoint connection

M2

second midpoint connection

M3

third midpoint connection

M.

Focus

MCF

Star point

Mp

Connection point

Mn

Connection point

N

Neutral point

N8

Neutral connection

NDc

negative output lead

PDC

positive output lead

P0 (t)

performance that varies over time

S1

Switching element

S2

Switching element

S3

Switching element

Scp +

controllable semiconductor valve

Scp-

controllable semiconductor valve

Scn +

controllable semiconductor valve

Scn-

controllable semiconductor valve

Nh3 +

controllable semiconductor valve

Nh3-

controllable semiconductor valve

Nh3

bidirectional switch

U

phase

Ux

Voltage source

U0

Output voltage

Urec

rectified voltage

ULp

first differential voltage

ULn

second differential voltage

UL3

third differential voltage

Uh3

Injection voltage

Ucp

Buffer capacitor voltage

Ucn

Buffer capacitor voltage

UMN

Center stress

V.

phase

W.

phase

Z1

first branch

Z2

second branch

Z3

third branch

Zm

Midpoint branch

Claims (25)

1. Rectifier circuit having a three-phase, six-pulse rectifier arrangement (1) of semiconductor valves (2), preferably a bridge rectifier circuit of diodes, with a load (6), wherein the rectifier arrangement (1) has a three-phase mains-side input (3) and a DC-side output (4) comprising three switching elements (S1, S2, S3) and a three-pole circuit (5), and each phase (U, V, W) of the mains-side input (3) can be respectively connected to a switching element (S₁, S₂, S₃) to form a first pole connection (A) of the three-pole circuit (5) for diverting an injection current (i_h3) into the three-pole circuit (5), and a second and third pole connection (B, C) of the three-pole circuit (5) is respectively connected to an output line (P_DC, N_DC) of the DC-side output (4) for control currents (i_cp, i_cn), wherein the three-pole circuit (5) is configured as a regulating circuit for actively regulating, independently of one another, at least two of the three currents (i_cp, i_cn, i_h3) given by control currents (i_cp, i_cn) and injection current (i_h3) so as to generate sinusoidal rectifier input currents and has controllable semiconductor valves (S_cp+, S_ep-, S_en+, S_cn-), preferably IGBTs, for actively regulating two of the three currents (i_cp, i_cn, i_h3) given by control currents (i_cp, i_cn) and injection current (i_h3), and a choke (7) is arranged on one of the output lines (P_DC, N_DC) of the DC-side output (4) between the second pole connection (B) and the load (6) or between the third pole connection (C) and the load (6) on the DC-side output (4), and the load (6) on the DC-side output (4) is a time-variable load (6), wherein the regulating circuit is configured to supply the injection current only in the phase that remains currentless due to operation of the six-pulse rectifier arrangement.
2. Rectifier circuit according to claim 1, wherein the second and third pole connection (B, C) of the three-pole circuit (5) is respectively connected to one of the two output lines (P_DC, N_DC) of the DC-side output (4) via a second and third inductor (L_cp, L_cn).
3. Rectifier circuit according to claim 2, wherein the first pole connection (A) is connected to the switching elements (S1, S2, S3) via a first inductor (L_h3), wherein the three inductors (L_h3, L_cp, L_cn)are formed by a three-leg choke.
4. Rectifier circuit according to any one of claims 1 to 3, wherein the two output lines (P_DC, N_DC) on the DC-side output (4) are connected to an output capacitor (C₀).
5. Rectifier circuit according to any one of claims 1 to 4, wherein each of the three phases (U, V, W) on the mains-side input (3) is respectively connected to a filter capacitor (C_F), wherein the filter capacitors (C_F) are star-connected together at a star point (M_CF).
6. Rectifier circuit according to any one of claims 1 to 5, wherein the three-pole circuit (5) is connected to the mains-side input (3) via at least one bypass capacitor (C_BF).
7. Rectifier circuit according to any one of claims 1 to 6, wherein the three-pole circuit comprises three converter systems (9, 10, 11) with controllable semiconductor valves (S_ep+, S_ep-, S_en+, S_en-) and/or a bidirectional switch (S_h3) , preferably arranged in a bridge structure, wherein the first pole connection (A) of the three-pole circuit (5) is provided on a first converter system (9), the second pole connection (B) of the three-pole circuit (5) is provided on a second converter system (10), and the third pole connection (C) of the three-pole circuit (5) is provided on a third converter system (11), and a connection to a branching point, a common centre point (M) of the three-pole circuit (5), is provided from all three converter systems (9, 10, 11).
8. Rectifier circuit according to claim 7, wherein the first converter system (9) is provided as a three-level bridge branch, wherein the second and third converter system (10, 11) are provided as a half-bridge, and the three converter systems (9, 10, 11) are formed by three parallel-connected branches (Z₁, Z₂, Z₃) equipped with electronic components, wherein the first pole connection (A) of the three-pole circuit (5) is formed on a first branch (Z₁), and the second and third pole connection (B, C) are formed on a third branch (Z₃), and each of the branches (Z₁, Z₂, Z₃) has a centre point connection (M₁, M₂, M₃), around which centre point connections (M₁, M₂, M₃) the components of the branches (Z₁, Z₂, Z₃) are symmetrically arranged, wherein a first centre point connection (M₁) of the first branch (Z₁) is connected to a second centre point connection (M₂) of the second branch (Z₂) via a bidirectional switch (S_h3), and the second centre point connection (M₂) is conductively connected directly to a third centre point connection (M₃) of the third branch (Z₃), wherein the third centre point connection (M₃) is provided as the centre point (M) of the three-pole circuit (5).
9. Rectifier circuit according to any one of claims 1 to 6, wherein the three-pole circuit comprises two converter systems (10, 11) with controllable semiconductor valves (S_cp+, S_cp-, S_cn+, S_cn-), preferably arranged in a bridge structure, wherein the second pole connection (B) of the three-pole circuit (5) is provided on a second converter system (10), and the third pole connection (C) of the three-pole circuit (5) is provided on a third converter system (11), and a connection to a branching point, a common centre point (M) of the three-pole circuit (5), is provided from both converter systems (10, 11), and the centre point (M) is connected to the first pole connection (A).
10. Rectifier circuit according to claim 9, wherein the second and third converter system (10, 11) are provided as a half-bridge, wherein the two converter systems (10, 11) are formed by two parallel-connected branches (Z₂, Z₃), and the first pole connection (A) of the three-pole circuit (5) is connected to a second branch (Z₂), and the second and third pole connection (A, B) are formed on a third branch (Z₃), and each of the branches (Z₂, Z₃) has a centre point connection (M₂, M₃), around which centre point connections (M₂, M₃) the components of the branches (Z₂, Z₃) are symmetrically arranged, and a second centre point connection (M₂) of the second branch (Z₂) is conductively connected directly to a third centre point connection (M₃) of the third branch (Z₃), wherein the third centre point connection (M₃) is provided as the centre point (M) of the three-pole circuit (5).
11. Rectifier circuit according to claim 10, wherein the second centre point connection (M₂) is connected to the first pole connection (A) via a voltage source (U_x).
12. Rectifier circuit according to claim 8, wherein two bridge valves (D_h3+, D_h3-), preferably diodes, are connected in series with the same conducting direction in the first branch (Z₁), wherein the first centre point connection (M₁) is arranged between the two bridge valves (D_h3+, D_h3-).
13. Rectifier circuit according to claim 8 or 10, wherein two buffer capacitors (C_CP, C_CN) are connected in series on the second branch (Z₂), wherein the second centre point connection (M₂) is arranged between the two buffer capacitors (C_CP, C_CN).
14. Rectifier circuit according to any one of claims 8 or 10, wherein the four controllable semiconductor valves (S_cp+, S_cp-, S_cn+, S_cn-)are provided on the third branch (Z₃) in a manner connected in series, wherein the centre point (M) of the three-pole circuit (5) is arranged in the connection between two series-connected pairs of the controllable semiconductor valves (S_cp+, S_cp-, S_cn+, S_cn-), and the second pole connection (B) is provided between the controllable semiconductor valves (S_cp+, S_cp-) of the first pair, and the third pole connection (C) is provided between the controllable semiconductor valves (S_cn+, S_cn-)of the second pair.
15. Rectifier circuit according to claim 12, wherein the two bridge valves (D_h3+, D_h3-) are configured as controllable semiconductor valves (S_h3+, S_h3-), preferably IGBTs.
16. Rectifier circuit according to claim 9, wherein the second and third converter system (10, 11) of the three-pole circuit (5) are formed with bidirectional three-level bridge branches which are known per se, preferably two so-called three-level neutral-point-clamped converters (3L-NPCs), wherein the three-level bridge branches are arranged symmetrically around a centre point branch (Zm) connected in parallel with the three-level bridge branches, and the centre point branch (Zm) is configured as two series-connected buffer capacitors (C_CP, C_CN), and the centre point (M) is provided between the two buffer capacitors (C_CP, C_CN), and a neutral connection (N₃) of the three-level bridge branch is connected to the centre point (M) and to the first pole connection (A), and an AC voltage connection (AC₈) of the three-level bridge branch are provided respectively as the second pole connection (B) and the third pole connection (C) of the three-pole circuit (5).
17. Rectifier circuit according to claim 9, wherein the three-pole circuit (5) is connected by the first pole connection (A) respectively to one side of two injection capacitors (C_h3p, C_h3n), which connection forms the centre point (M) of the three-pole circuit (5), wherein the two other sides of the injection capacitors (C_h3p, C_h3n) are connected via a voltage source (U_x) and form connection points (M_P, M_N), wherein, starting from each of the connection points (M_P, M_N), a current loop is provided which in each case has a buffer capacitor (C_CP, C_CN) and a pair of controllable semiconductor valves (S_cp+, S_cp-, S_cn+, S_cn-), and the second pole connection (B) and the third pole connection (C) is provided between the respective two controllable semiconductor valves (S_cp+, S_cp-, S_cn+, S_cn-)of a pair.
18. Method for impressing control currents (i_cp, i_cn) in a DC-side output (4), which comprises three switching elements (S1, S2, S3) and a three-pole circuit (5), of a rectifier circuit according to claim 1 having a three-phase, six-pulse rectifier arrangement (1) of semiconductor valves (2), preferably a three-pole bridge rectifier circuit of diodes, with a load (6), wherein an injection current (i_h3) is branched off from at least one of the three phases (U, V, W) on a mains-side input (3) of the rectifier circuit, characterized in that the injection current (i_h3) is supplied to a first pole connection (A) of the three-pole circuit (5), and at least two of the three currents (i_cp, i_cn, i_h3) given by control currents (i_cp, i_cn) and injection current (i_h3) are actively regulated independently of one another by means of active components, preferably controllable semiconductor valves (S_cp+, S_cp-, S_en+, S_cn-), in the three-pole circuit (5) so as to generate sinusoidal rectifier input currents, wherein the injection current is supplied only in the phase that remains currentless due to operation of the six-pulse rectifier arrangement, and a control current (i_cn, i_cp) is respectively added to the rectifier currents (i_p, i_n) on two DC-side output lines (P_DC, N_DC) of the DC-side output (4) via a second and third pole connection (B, C) of the three-pole circuit (5), and one of the rectifier currents (i_p, i_n) with the control current (i_cn, i_cp) respectively supplied thereto is guided through a choke (7) arranged between the second pole connection (B) and the load (6) or between the third pole connection (C) and the load (6) on the DC-side output (4).
19. Method for impressing control currents (i_cn, i_cp) according to claim 18, characterized in that the injection current (i_h3) and/or the control currents (i_cp, i_cn) are guided through at least two of three inductors (L_h3, L_cp, L_cn), provided on at least two of the three pole connections (A, B, C) for smoothing and controlling the currents (i_h3, i_cn, i_cn), by differential voltages (U_L3, U_Ln, U_Lp) across the inductors (L_h3, L_cp, L_cn), and the third current (i_h3, i_cn, i_cp) is set by regulating two of the three currents (i_h3, i_cn, i_cp).
20. Method for impressing control currents (i_cn, i_cp) according to any one of claims 18 to 19 using a rectifier circuit according to any one of claims 7, 8 or 12 to 17, characterized in that a centre point voltage (U_MN) is measured between the centre point (M) of the three-pole circuit (5) and a neutral point (N), and a mean value of the centre point voltage (U_MN) is regulated using one of the converter systems (9, 10, 11).
21. Method for impressing control currents (i_cn, i_cp) according to claim 20, characterized in that the mean value of the centre point voltage (U_MN) is regulated to zero.
22. Method for impressing control currents (i_cn, i_cp) according to claim 20 or 21 using a rectifier circuit according to any one of claims 13 to 17, characterized in that a first buffer capacitor voltage (U_CP) across the buffer capacitor (C_CP) is regulated to be greater than a voltage of the positive output line (P_DC) against a neutral point (N), and a second buffer capacitor voltage (U_CN) across the buffer capacitor (C_CN) is regulated to be lower than a voltage of the negative output line (N_DC) against the neutral point (N).
23. Method for impressing control currents (i_cn, i_cp) according to any one of claims 20 to 22, characterized in that the regulation of the mean value of the centre point voltage (U_MN) takes place by means of the controllable semiconductor valves (S_cp+, S_cp-, S_cn+, S_cn-).
24. Method for impressing control currents (i_cn, i_cp) according to claim 19 to 23 using a rectifier circuit according to claim 15, characterized in that a first buffer capacitor voltage (U_CP) across the buffer capacitor (C_CP) is minimized, and a second buffer capacitor voltage (U_CN) across the buffer capacitor (C_CN) is minimized, wherein the centre point voltage (U_MN) is regulated to the negative half-value of an injection voltage (U_h3) , and the injection voltage (U_h3) is applied between the first pole connection (A) and the neutral point (N) .
25. Method for impressing control currents (i_cn, i_cp) according to any one of claims 19 to 24 using a rectifier circuit according to claim 11 or 17, characterized in that the potential of the centre point voltage (U_MN) relative to one of the two output lines (P_DC, N_DC) is increased or reduced through the regulation of the voltage source (U_x).

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